1. Field of Invention
This invention pertains to an auto-locking belay safety mechanism which improves the safety characteristics of an auto-locking belay device. In particular, it pertains to a mechanism that will cause a rope to be locked against passage through an auto-locking belay device even if the belayer panics after having overridden the locking mechanism within the auto-locking belay device.
2. Description of Prior Art
In the sport of rock climbing, a belay device is used to protect a climber. The person operating the belay device is known as the belayer. A climbing rope, one end of which is attached to the climber, runs through the belay device which is anchored near, or attached directly to the harness of, the belayer. The belayer can control the rate of movement of rope through the belay device and, if the climber falls, the belayer can stop the rope using the belay device, thereby stopping the fall of the climber.
There is a class of belay devices known as auto-locking belay devices. Such devices need no action on the part of the belayer to stop the rope in the event of a fall by the climber. If a climber falls, the forces of the rope on an auto-locking belay device cause the belay device to lock the rope. Unfortunately, these devices also tend to lock the rope when a belayer attempts to quickly feed rope out to the climber. This is because the act of feeding rope rapidly through the device yields approximately the same rope forces on the belay device as those experienced when a climber falls. The belayer, therefore, often has to temporarily override the normal function of an auto-locking belay device in order to rapidly feed rope through the device to the climber. Auto-locking belay devices therefore contain a means to override the normal function of the device. If a climber falls when the belayer has overridden the normal function of an auto-locking belay device, the belayer should release his hold on the device, thereby canceling the override function and allowing the belay device to function normally so as to lock the rope and stop the fall of the climber. Occasionally, a belayer will panic and actually grab the auto-locking belay device tighter, rather than releasing the device, when a climber falls while the belayer has overridden the normal function of the auto-locking belay device. In this situation, the instinct of the belayer is to grab harder, as if that would stop the rope, when in fact that action does not allow the override function to be cancelled and therefore allows the rope to continue to pass through the belay device. The result can be harmful or fatal to the climber since the fall is not stopped.
The subject Safe Auto-Locking Belay Override Mechanism solves a very dangerous problem of auto-locking belay devices by canceling the override function even if a belayer panics, as described above, during the fall of a climber. A novel and unobvious aspect of the invention relies on the fact that the belayer actually grabs the device tighter when he panics. The subject invention therefore consists of an override mechanism that responds differently to different force levels from the belayer, and to three force levels in particular. If there is minimal or no force exerted on the Safe Auto-Locking Belay Override Mechanism by the belayer, the auto-locking belay device's normal function will not be overridden and the auto-locking belay device can therefore lock the rope if the rope forces are sufficient to lock it, such as during a fall of a climber. If there is an intermediate amount of force exerted on the Safe Auto-Locking Belay Override Mechanism by the belayer, such as during the times when a belayer needs to feed rope through the belay device, the normal function of the auto-locking belay device will be overridden and therefore the rope will not be locked against movement through the auto-locking belay device. If, however, there is a high amount of force exerted on the Safe Auto-Locking Belay Override Mechanism by the belayer, such as when the belayer panics, the override function will be cancelled thereby allowing the auto-locking belay device to function normally and to lock the rope if the rope forces are sufficient such as during a fall of a climber.
Although there are many different styles of auto-locking belay devices, they all function by locking the rope against further movement if the rope exerts sufficient force on the device such as would occur when a climber falls, and they all have a means to override this normal function such that rope can be fed quickly through the device by the belayer when it is advantageous to do so. Much of the relevant prior art deals with descenders, devices which function like auto-locking belay devices but with the primary purpose of allowing a person to descend a rope. Examples of the prior art include U.S. Pat. No. 5,054,577 to Petzl et. al., U.S. Pat. No. 5,076,400 to Petzl et. al., U.S. Pat. No. 5,360,083 to Hede, U.S. Pat. No. 5,577,576 to Petzl et. al., U.S. Pat. No. 5,597,052 to Rogleja, U.S. Pat. No. 5,850,893 to Hede, and U.S. Pat. No. 6,029,777 to Rogleja. A very popular commercially available auto-locking belay apparatus is the GRIGRI made by the Petzl company of Crolles, France. None of the aforementioned examples of the prior art disclose, teach, or illustrate the unique function and use of the subject invention.
The potential safety problem with the override mechanism of auto-locking belay devices of the prior art is well known by those experienced in the art. Prior to the subject invention, attempts to mitigate this problem have focused on the physical interaction between the rope and the belay device, rather than on the realization that the belayer actually exerts greater force on the override mechanism when he panics while the override mechanism is activated. For example, the GriGri contains a locking cam that is biased against movement by a spring. The purpose of the locking cam is to lock the rope if sufficient rope forces are present to rotate the cam. The purpose of the spring, that biases the cam against movement, is to allow the belayer to feed rope through the device without having to override the normal function of the device. Although this works during cases when the belayer can feed the rope slowly and steadily through the device, it does not work in the case that the belayer needs to feed rope quickly through the device. If a belayer needs to feed rope quickly through the GriGri, he must still override the normal function of the GriGri in order to do so.
The concept of the subject Safe Auto-Locking Belay Override Mechanism, which responds differently to three different belayer force levels, can be applied to render any of these prior art auto-locking belay devices much safer; but the particular embodiment of the invention will be different depending on the design of the auto-locking belay device for which it is intended. The particular embodiments of the Safe Auto-Locking Belay Override Mechanism described and illustrated herein are for an auto-locking belay device which operates based on a rotating locking cam, such as the device illustrated in U.S. Pat. No. 5,076,400 to Petzl et al. The subject invention is intended, however, to cover all embodiments which utilize the novel concepts described above, not just the particular embodiments illustrated.